The best way to sequester carbon in the ground would be to use grasslands and large herds of herbivores - this is far larger quantities of carbon than anything we can artificially use, and it would cost FAR less.

Also, we know that we have to stop burning all fossil fuels as quickly as possible if we are to avoid the worst effects from climate change. Because, we have already put way too much carbon into the atmosphere, and IF we can sequester some of what is already out there, then that helps - but we have to also stop putting more additional carbon into the air.